Manufacture of aliphatic acids and esters



Patented as. as, .1932

UNITED STATES ENGLAND, A SSIGNOBS '10 OF DELAWARE PATENT A macrunsoramnarrcacmsm p n Drawing. Application fled September 21, 1 92s, Serial Io. 188,118, aim in Great 31-min a so, me.

This invention relates'to the manufacture of acetic acid and other aliphatic compounds.

The specification accompanyin U. S. patcnt application S. No. 112,166 of fienry Dreyfus describes catalytic processes for the synthetic production of acetic acid from mixtures of carbon monoxide and hydrogen. The specification accompanying ent application S. No. 112,165 of enry Dreyfus escribes processesfor producing acetic acidand acetone'bysubj mixtures of carbon monoxide and methyl alcohol to the expressed by the equation pable of action of heat in the presence of ca capable of. forming acetates whichsplit off acetic acid or acetone or both acetic acid and acetone at elevated temperatures not exceedv ing about Mm 450? C.

' We have now discovered that acetic acid can be produced by the action of carbon mon.

" oxide on methyl alcohol in the presence of in-,

organic acid catalysts. ,The reaction can be CO+ GH OH= CILCOOH -wholl or partly generated from or replaced by su 'ances or mixtures of substances ca pable in t e presence of carbon monoxide of being converted into acetic acid or methyl acetate under theconditu'ons of the reaction, as hereinaftermore fully described. 7

The operation can be performedat atmospheric pressure, but proceeds. more rapidly at inci eased-pressures. The pressure may be as high as 100, 200 or 300 atmospheres or any high'erpressure that can convenien llb attained in ractice. Therange of temperae tures us yv employed is from about 200 250 (14:0 about 400M50 0., temperatures of 300 to 400 C. be1n g preferably ado ted. Preferably a catalyst that isnon-volatile or otherwise chemically U. S. pat-- catal reduce According to the prevailing conditions-the one or more methoxy.

glenerating methylalcohol, and ca'- only very slightly volatile under the conditions of the reaction is used. It is desirablemaximmus, or LOIIDOZI'AID wan-rm; man, or sroimolr, pm nmir, conrona'nor or amma, 4 oonroaa-rron that the catalyst should not be reduced or V changed during the reaction into a non-acid or volatile bod Particularly results are obtained with phosphorus derivatives, such a the acids derived from phosphorous, and especially the phosphoric acids, forinstance, ortho, pyro or meta phosphoric acid, or of these ac1ds. Boric acid, 7 arsenic, and phosphomolybdic acid are also suitable for use as ysts. Mixtures containing two or more of the aforementioned catalysts may also be employed.

. When acids are used as catalysts, they may be partially neutralized to form acid salts if desired, tho honlyto such an extent that the resul at the temperature of the reaction, contains free hydroxyl groups according -to the usual formulation. A partial neutralization of the acid is particularly advan us in cases where it is desired to e volatility ofjhe acid or to convert it into the solid form. For instance, we

may use a compound which may be regarded as consisting' 0 one. molecule of a monovalent base, or its equivalent of a in combination with more 7 of ortho phosphoric acid, so that the resul complex phosphorus derivative is still aci at tem eratures between 300 and 400 0., or other temperature used in the reaction.

polyvalent base,- thanone molecule Thus, for instance, in accordance with the present invention, an acid aluminium phoshate of'the composition Al=O,;12H,PO may employed as catalyst. The catalyst used may be in the liquid state,

as in the case offphosphoric acid, or in the solid state, as-in the caseof boric acid or -acid aluminium phosphate, at the temperaof the reaction, and maybe distributed tIlIe over or an ported on an inert solid carrier,

for examp e, coke,

lysts may be Into the reaction chem-- before the of the operation,

or maybe added during the operation, for ex; 7

catalyst, or in 7 some cases in the form of vapour of a volatile ample, as a spray, of a liqui ester for a methyl which is dephite, etc. The catacomposed under theconditions of the reaction to yield an acid cataly t, or may be introduced into. or generated in the reaction chamber in any other way.

The carbon monoxide can be introduced.

either as such or in the form-of industrial or other mixtures with hydrogen and/or inert ases, for example,-nitrogen, methane, etc.

hus, we may use water gas, roducer gas or coke oven gas, but it is pre erable to use carbon monoxide alone.

The methyl alcohol may be replaced by dimethyl ether, the product of the reaction appearing as methyl acetate or, if water is.

It is interesting to note that, in the case of methyl formate, the reaction appears to involve the formation of carbon monoxide and methyl alcohol by decomposition of the methyl formate, the carbon monoxide afterwards combining with the methyl alcohol in the presence of the acid catalysts. In any case the net result of the dpass e of the methyl formate over the aci cata yst is the conversion of the methyl formate into its .isomer acetic acid.

It will be seen that it ispossible. in accordance with this invention to use substances for example, methyl formate-which in themselves provide both of the essential elements for the reaction, since they are ca'able of yielding methyl alcohol an carbon monoxl e. I I p Thus it is possible to'obtain acetic acid :without the use of pressure by conducting vapours of I methyl alcohol over the catalyst at about 350 to 450? C., the carbon monoxide being supplied by the breakdown of a art; of the me yl alcohol'to carbon monoxide ndhydrogen. i

Of course the choice of the raw materials used, and of the conditions employed, will depend on the prevailing circumstances. Usu-' v ally it is preferable when -,using methyl alcohol to conduct the operation under pressure and to select the other conditions of the reaction so as to minimize the breakdown; of methyl alcohol.

Instead of starting with methyl alcohol as such or in the formQof dimethyl'ether .or

methyl esters, we may employ mixtures. of substances which are capable of-being com bined to form' methyl alcohol, and particu larly mixtures of carbon monoxide and hydrogen. For example, water gas may be conovert ed into methyl alcohol by the action of heat and pressure in the presence of zinc oxide or other suitable catalyst. The resulting products are led without cooling direct to a chamber containing an acid catal st for conversion into acetic acid. Prefera ly the carbon monoxide necessary for the conversion of the methyl alcohol into acetic acid is present in theinitial mixture of carbon monoxide and hydrogen, the quantity of carbon monoxide in such case being in excess of that necessary-for the formation of methyl alcohol.

:The necessary proportion of carbon monoxidemay however be incorporated in the gaseous mixture immediately before it is passed over the acid catalyst. The reaction takes place in two stages, represented by the following equations:

CO+2H =GH OH CH OH+CO=CH CObH We have also found that the preliminary "treatment for the production of methyl al-v 9 cohol as a separate productman be eliminated. Acetic acid can thus. be obtained by passing a mixture of carbon monoxide and hydrogen in the requisite proportions over an acid catalyst. In this case, the reaction can be regarded as taking place in two stages involving the production'of methyl alcohol and the simultaneous transformation of the methyl alcohol into acetic acid, or may be represented more simply as occurring in a single stage according to the following equation:

' 200 2H CH COOH However it is preferable to use previously prepared methyl alcohol or dimethyl ether or a methyl ester in conjunction with carbon monoxide. j

Conveniently, theprocess is carried out in a continuous manner by mixing carbon monoxide, or water gas, or other gas containing carbon monoxide, with the vapour of methyl alcohol or dimethyl ether or methyl formate or acetate, and passingthe mixture into a reaction chamber contalning the acidcatal st in liquid or solid form, the reaction cham r heated: to a temperature of about 250 to 45U CL, and preferably between 300 and 400 C., but the invention is not limited in this respect; 7 According to one form of methyl alcohol is prepared by bubbling carbon monoxide or a gas containing the same through a heated "vessel containing methyl alcohol and is brought into contact with the acid catalyst. However, the methyl alcohol, dimethylether etc. may be introduced in the form of vapour or spray and mixed .with the carbon monoxide or gas containing the same, or any other suitable procedure may be adopted.

the invention, a m xture of carbon monoxi e and the vapour ture favours the formation The presenceof water in the aseous mix- 7 free acetic acid, particularly when dimethyl'ether-or .methyl esters or similar bodies are em loyed in place of -or together with methyl a cohol.-

When methyl alcohol or its derivatives are used as starting material, the reaction can take place at ordinary pressure but is preferably effected under pressure which since underthese conditions, the formation of undesirable decomposition products is minimized or prevented. I

- As previously stated, the acetic acid formed vmay be obtained either in the freestate or in the form of the methyl ester which is formed by condensation ofthe acetic acid with the methyl alcohol present in the reaction chamber. Thereaction can be so directed so as to give methyl acetate practically exclusively. The production of methyl acetate is favoured by the presence of excess of methyl alcohol in the reaction chamber and theabsence of water or the use of only small amounts of water. If however no excess of methyl alcoholisused,

and water is presentin sufiicient quantities,

acetic acid is obtained, while mixtures of acetic acid and methyl acetate .in various prothe conditions adopted.

' portions can be obtained in accordance with When methyl formate is used a so-called isomerization to acetic acid'takes lace.

If the acetic acid obtained by this process is intended for the manufacture of acetone, the gases issuing from the reaction chamber may without cooling be brought into contact with acetone-forming catalysts. For example, the reaction products may be led directl over mangoanous oxide at temperatures of 400- 500 i If the oper'ation'is so conducted as to produce substantial quantities of methyl acetate, themethyl acetate so' obtained may be easily saponified andworked up into acetic acid and methyl alcohol or dimethyl ether-,tha two latter being returned for recirculation through the'plant for conversion into acetic The process can be carried into efiectin many different ways, and we do not restrict our invention to the following examples of,

forms of apparatus and methods of procedure, said examples being given byway of explanation and being in no way limitative ii rdin thod f rf rmmgthe cco gtooneme o pe o "invention, we use a closed train of apparatus comprising a gas circulating pump, which drives the carbon monoxide or gas mixture containin carbon monoxide first through a mixing c amber, where dimethyl ether, methyl alcohol, etc., and/or water maybe incorporated with the gas in the form of vapour or where the composition of the gas may be adjusted (eygQby adding hydrogen). The

resulting gaseous mixture then passes through .a heat exchanger into the reaction chamber. The products issuing from the reaction chamber pass through the heat exchanger to a condenser rovided with'a receiver, in which the uncon ensable gases are separated from the liquid products. The liquid products are withdrawn and the gases'are returned to the gas circulating pump. This circuit may be supplemented by pressure gauges, traps for acid, preheaters, flow meters, temperature controls, and so on.

The reaction chamber may contain any device which will bring the gas well into contact with the catalyst. For instance in case of a liquid the gases may be bubbled through the liquid or the reaction chamber may be arranged as a washing column, or it may be fitted with agitators, orit may be rotary, and

if desired provided with carrier material for the liquid. If the catalyst be a solid, or a liquid spread on a solid carrier, it is advantageously used in granular form.- It is preferable to employ a large mass ofa liquid catalyst. 5

Both the catalyst and the gases should be. reasonably free of such impurities as would neutralize the acid.

The'difieren't parts of the apparatus are preferabl protected against corrosion by acids an carbon monoxide. Thus, for example, itis preferable to avoid the exposure of the gases to the action of iron in' the syst m, although special. alloys that will not orm iron carbonyl can be used with advantage, The vessels containing or in contact with acids are preferably suitably protected, according to the kind of acid present. For instance, the parts in contact with acetic acid may be made of, or lined with, copper, while those containing phosphoric'acid may have a lining of graphite or gold, or may be made of, or lined with "copper. In using copper in contact withphosphoric acid it is preferable to prevent the access of oxygen to the apparatus. i The process of the 'saponification of fatty acid esters so as to obtairi concentrated fatty acids forms the subject matter of application No. 295,611; while the manufacture of acetic- .acid bysubjecting .a mixture of carbon monoxide, and hydro on to the action of an im organic acid ca yst forms the subject matter of a .divisional application No, 347,448

limited in any way thereto.

filed March 15 1929.

The following exam les 'illustrate sometechnical applications 0 our process, but as will be understood the invention is 'not Example 1 Carbon monoxide at about 100-180 atmospheres pressure is bubbled through methyl alcohol containing about 520% of water and heated to about (SO-80 0., and the resulting mixture of gases and vapours is passed through a reaction chamber heated to about 300-400 O. The reaction chamber maybe filled with coke or graphite soaked in phosphoric acid or with acid aluminium phosphate, or may take the form of a slowly rotating chamber which is about one-third full of phosphoric acid and is filled with graphite pebbles or other materials presenting an extended surface. The acetic acid produced is condensed preferably at low temperatures and if necessary, redistilled, the uncondensed gases being returned for recirculation and urther treatment in the system.

In this example if a sufficiently large excess of carbon monoxide is used, the reaction can proceed in the presence of very small quantities of water or in the absence of water. The methyl alcohol can also be separately vaporized in any way, and the resulting vapours mixed with the carbon monoxide.

I Example 2 Anhydrous methyl alcohol is substitute I for methyl alcohol containing water in the Example 3 I A mixture of about -65% by voluriie of carbon monoxide with about 35-45% by volume of hydrogen is passed under a pressure of about150-2O0 atmospheres through avessel containing zinc oxide and kept at a temperature of about 3004 00 C. The resultin mixture containing carbon monoxide an methyl alcohol vapouris'passed without cooling over an acid catalyst maintained at about 300400 C. The reaction roducts'are separated and the uncondensa le gases are returned for re-circulation through thesystefn.

I Etvample 4 j p Purified water gas is compressed to 250-300 atmospheres and after bubbling through wa-.

ter at a temperature of about 100I150 C. is passed through a chamber maintainedat a I 'tures between 180 and 220. C. being mamas and the condensate is collected and redistilled to obtain the acetic acid. The'nitrogen and other inert gases that accumulate in the system are removed either, intermittently or continuously and replaced by. fresh supplies of water gas. p In either oftheExamples- 1 .and 2, themethyl alcohol may be replaced by dimethyl ether, methylformate or methyl acetate, or mixtures of these bodies with each other. or with methyl alcohol, provided that these substances or their vapours are mixed in the appropriate proportions with the carbon monon e.

As previously stated, the-process may be directed to the'manufacture methyl acetate 'as' practically sole product of the "reaction. In this case, ifacetic acid is desired as ulti mate product, the methyl acetate is saponified and the methyl "alcohol or dimethyl ether acid, for example, phosphoric .acid or sulphuric acid, being-preferably used as's'aponifying agent.

simultaneously producedis re-circulated The reaction proceeds accordixig to the following equation:

2cH,ooo.oH,+-H.o=

- 2orLcooH+ 011.).0

It is preferred to use phosphoric acid as saponifying agent, since it does not act as an oxidizing agent at the'temperature employed. The reaction takes place at temperatures between about 150 and about'300 C., temperaespecially advantageous. For instance, at 200 C. the reaction proceeds rapidly, and results in substantiall a quantitative yield.

The more highly hydrated forms of hos pho'ric acid, for instance ortho phosp oric acid and pyrophosphoric acid, are capable of supplying the water required for the saponification, bein themselves at the same time dehydrated to t e form of meta phosphoric acid. It is therefore possible to perform the reaction ina continuous manner, by continuously introducing supplies ofester and water in the acid, the p osphoric acid serving m requisite roportions into the ph horicect as a carrier for;the water.

. The saponification may carried out in any apparatus designed for the interaction of gas and liquids, for example, wash towers," mixers,.b ubblers, etc.

a The saponification of the methyl aceta may be carried out continuously with its production. Thus for instance a mixture of carbon monoxide and methyl alcohol vapour may be'passed under pressure over phosphoric acid at 300-400 (1., and the products of reaction containing methyl acetate, preferably expanded to lower pressures, for instance, atmospheric pressure are passed togetherwith the requisite quantity of. steam through a chamber containing phosphoric acid maintained at lower temperatures, for example, 180-250 C.

It will be seen from the foregoing descrip-' tion that the same catalyst, for example, phosphoric acid, can be used under diiferent conditions to produce methyl acetate and to convert the methyl acetate into acetic acid and dimethyl ether. The acetic acid can be con densed and the dimethyl ether, which is gase ous at ordinary temperatures can be returned for admixture with further quantities of carbon monoxide for conversion into acetic acid.

The methyl acetate is however, preferably separated from the uncondensable gases with which it is mixed and is converted by a separate operation into glacial acetic acid and dimethyl ether. 7.

The following examples will illustrate this method of saponification, but we do not restrict our invention to these particular methods.

' Example 5 A closed copper vessel of high cylindrical shape with a quick running agitator of thepropeller type is nearly filled with phosphoric acid and kept by outside heating at 180220 The vapour of methyl acetate is intro duced near the bottom of the vessel, and also the required amount of steam, while'the top is connected to a condenser and receiver; The gas escaping from the receiver is pure methyl ether- The condensate is glacial acetic acid, with more or less unchanged methyl acetate, which is easily ofl.

Example 6 containing'copper plates ar-' A wash tower,

ranged in the usual manner,

- 180200 C. and phosphoric acid is run through it from top to bottom. The acid is circulated back to the top by a steam jet,

-w hich also acts as a hydrating agent.

Methyl acetate vapour is led up the tower in counter current to the hydrated acid. The products are the same as in Example 1.

The invention is not to any of the particular embodiments, whether of the reaction or of the subsidiary described but may be pe methods falling within 10 l reactions, herein rformed-by any other the scope of the fola It isto be understood that though certain ranges of temperature and other conditions e herein mentioned as those preferred for use with certain catalysts and certain raw materials the invention is not limited in these respects. The temperatures used in any par! ticular case are preferably those which are found by experience to give a maximum yield of acetic acid or methyl acetate with a mini- 'mum amount of undesirable by products.

Thus if a catalyst that is decomposable at high temperatures is employed, for instance an inorganic acid containing organic groups, the reaction is conducted at suitably lower temperatures and at appropriate conditions of pressure, etc. so as to prevent or modification of the catalyst to an inactive form.

Observing similar precautions as to tem' perature, pressure, etc. it is also possible to'extend the process to the treatment f higher a1 cohols, for instance, ethyl alcohol, etc., or their ethers or other appropriate derivatives, for" the production of higher acids, for instance, propionic acid, or their corresponding esters.

What we claim and desire to secure by Letters Patent is 1. Process for the manufacture of compounds'containing the acetyl group whichcomprises subjecting methyl alcohol to the 7 action of carbon'monoxide in the resenoe of an inorganic acidic catalyst conta ning at least one acidic hydroxyl group directly linked to a non-metallic element.

2. Process for the manufacture of compounds containing the acetyl group which comprises subjecting methyl alcohol to the action of carbon monoxide in the presence of a phosphoric acid. 4

3. Process for the manufacture of compounds containing the acetyl group which 7 comprises subjecting methyl alcohol to the action of carbon monoxide pyrophosphoric acid.

4. gocess for thiehmanufaicture of un containing e acety up w mprises subjec methyl al c oliol to the action of carbon monoxide in the resenco of an inorganic acidic catalyst containing at least. one acidic hydroxyl group directly in the presence of linked to a non-metallic element at temperatures between about-200 C. and about 450 .G., and under pressure.

5. v for the manufacture of compounds containing the acetyl group which comprises subjecting methyl alcohol to the action of carbon monoxide in the presence of a phosphoric acid. at temperatures between about 200C. ,and about 450 C.,and under 1 pressure.

of a phosphoric acid at temperatures between about 200 C. and about 450 0., and under pressure of more than 50 atmospheres.

7. Process for the manufacture of compounds containing the acetyl group which comprises subjecting methyl alcohol to. the

action of carbon monoxide'in the presence of a phosphoric acid at temperatures between about 300 C. and about 400 C., and under pressure of more than 50 atmospheres.

8. Process for the manufacture of compounds containing an alkacyl group which comprises subjecting an aliphatic alcohol of the formula to the action of carbon monoxide in the presence of an inorganic acidic catalyst containing at least one acidic hydroxyl group directly linked to a nonsmetallic element.

9. Process for the manufacture of compounds containing an alkacyl oup which comprises subjecting an aliphatic alcohol of the formula to the action of carbon monoxide in the presence of a phosphoric acid.

10. Process for the manufacture of compounds containing an alkac l oup which the formula (L m1) OH to the action of carbon-monoxide in the presence of pyrophosphoric acid.

11. Process for the manufacture of compounds containing analkacylgroup which comprises subjecting an aliphatic alcohol of the formula 4 one...) on

12. Process for the manufacture of com pounds containing an alkacyl oup which comprises subjecting an aliphatic alcohol of the formula v one...) OH

to the action of carbon monoxide in the presence of a phosphoric acid at temperatures between about 200 C. and about 450 (3., and under pressure.

13. Process for the manufacture of com-' pounds containing an alkacyl group which comprises subjecting an alkoxy compound to the action of carbon monoxide in the presence of an inorganic acidic catalyst containing at least one acidic hydroxyl group directlyllinked to anon-metallic element.

14. Process for the manufacture of compounds containing an alkacyl group which comprises subjecting an "alkoxy compound to the action of carbon monoxide in the presence of an inorganic acidic catalyst containing a least one acidic hydroxyl group di-v rectly linked to a non-metallic element at temperatures between about 200 C. and 450 C., and underpressure/ v j 15. Process for the manufacture of compounds containing the acetyl 'group' which comprises subjecting a compound containing a methoxy group to the action of carbon monoxide in the presence of an inorganic acidic catalystcontaining at least one acidic hydroxyl group directly linked to a nonmetallic element.

16. Process for the manufacture of compounds containing the acetyl group which directly linked to a non-metallic element. comprises subjecting an ahp atic alcohol of v 18. Process for the manufacture of compounds containing an alkacyl group which comprises subjecting an alkyl derivative of water to the action of carbon monoxide. in the presence of a phosphoric acid at temperatures between. about 200 C. andabout 450 0., and under ressure.

19. Process or the manufacture of compounds containing the acetyl group which vcomprises subjecting a methyl derivative of water to the action of carbon monoxide in the presence of an inorganic acidic catalyst containing at least one acidic hydroxyl group directly-linked to a non-metallic element.

20. Process for the manufacture of compounds containing the acetyl group which comprises subjecting a methyl derivative of water to the action of carbon monoxide in the presence of a phosphoric acid-at temperatures-between about 200 C. and about 450 0., and under pressure.

21. Processfor the manufacture of compounds containing the acetyl. group which comprises subjecting methyl alcohol and dimethyl ether to the action of carbon monoxide in the presence of a phosphoric acid at temperatures between about 200 C. and 5 about 450 (3., and'under pressure.

22. Process for the manufacture of acetic acid which comprises bringing a gaseous mixture of methyl alcohol, carbon monoxide tween about 200 C. and about 450 C., and

aeeaeaa and water into contact with an inorganic acidic catalyst containing at least one acidic hydroxyl group directly linked to a non-metallic element at temperatures beunder pressure.

' 23. Process for the manufacture of acetic acid which comprises bringing a gaseous mixture of methyl alcohol, carbon monoxide and water into contact with a phosphoric acid at temperatures between about 200 C.

and about 450 0., and under pressure.

24. Process for the manufacture of acetic acid which comprises bringing a gaseous mixture of a methoxy compound, carbon vmonoxide and water into contact with an inorganic acidic catalyst containing at least one acidic hydroxyl group directly linked to a non-metallic element at temperatures between about 200 C. and about 450 ,C., and under pressure. a V

25.. Process for the manufacture of acetic acid which comprises bringing a gaseous mixture of a methoxy compound, carbon monoxide and water into contact with a phosphoric acid at temperatures between about 200 6. and about 450 C., and under pressure. 4

26. Process for the manufacture of a. fatty acid which comprises bringing a gaseous mixture containing an aliphatic alcohol, carbon monoxide and water into contact with an inorganic acidic catalyst containing at least one acidic hydroxyl group directly linked to a non-metallic element at temperatures between about 200 C. and about 450 (l, and under pressure.

27. lProcess for the manufacture of a fatty acid which comprises bringing a gaseous mixture containing an aliphatic alcohol, carbon monoxide and water into contact with a phosphoric acid.

28.- A cyclic process for the manufacture of acetic acid which comprises subjectin a methyl derivative ofwater to the action- 0 carbon monoxide in the presence of an inorganic acidic catalyst containing at least one acidic 'hydroxyl group directly-linked to a non-metallic element, converting the methyl acetate content of the reaction product into free acetic acid by saponification in the pres- ,ence of substantially the quantity of water necessary for the production of glacial acetic acid and dimetliyl; ether, .and returning the dimethyl ether to react with carbon 'monox:v

ide.

of acetic acid which comprises subjecting a 29. cyclic processforthe manufacture I methyl derivative of water 'to the action of carbon monoxide in the presence of an inor-.

ganic acidic catalyst containing at least one acidic hydroxyl group directly linked to a 1 non-metallic e ement, converting the methyl acetate content of the reaction product into {I free acetic acid by saponification with phos- 

